{-# LANGUAGE MultiParamTypeClasses,
			 TypeSynonymInstances,
			 FlexibleInstances,
			 FunctionalDependencies #-}
-- |
-- Module       : Test.Hspec.Attoparsec.Source
-- Copyright    : (c) 2014 Alp Mestanogullari
-- License      : BSD3
-- Maintainer   : alpmestan@gmail.com
-- Stability    : experimental
-- 
-- A 'Source' class that ties parser types and input types to
-- give you a uniform interface for testing your parsers,
-- without caring about the input type.
module Test.Hspec.Attoparsec.Source where

import qualified Data.Attoparsec.ByteString as AB
import qualified Data.ByteString as B

import qualified Data.Attoparsec.ByteString.Lazy as ALB
import qualified Data.ByteString.Lazy as LB

import qualified Data.Attoparsec.Text as AT
import qualified Data.Text as T

import qualified Data.Attoparsec.Text.Lazy as ALT
import qualified Data.Text.Lazy as LT

import qualified Data.Attoparsec.Types as Atto

import Data.String (IsString)

-- | A class where each instance will just teach
--   how to get an Either or the specific result 
--   type associated to the parser for the given
--   input type.
class (Eq string, Show string, IsString string)
   => Source parser string string' result | string -> parser, string -> result, string -> string' where
        -- | Feed some input to a parser and extract the result
        --   as either a failure 'String' or an actually parsed value.
        --   Can be read as /fed to/.
        -- 
        -- > -- "<a ...>" fed to an HTML parser 
        -- > "<a href=\"/foo\">Go to foo</a>" ~> htmlParser :: Either String a
        (~>) :: string -> parser string' a -> Either String a

        -- | Feed some input to a parser and extract it as the
        --   appropriate result type from that module.
        -- 
        --   This is not currently useful in the library per se,
        --   but is used in test-suites directly where we generally only deal
        --   with one concrete set of parser, input and result types.
        --   This lets us inspect the result in any way we want, e.g
        --   in conjunction with @shouldSatisfy@ or a custom hspec combinator.
        (~?>) :: string -> parser string' a -> result a

instance Source Atto.Parser B.ByteString B.ByteString AB.Result where
        t ~> p = AB.parseOnly p t

        t ~?> p = AB.parse p t

instance Source Atto.Parser LB.ByteString B.ByteString ALB.Result where
        t ~> p = ALB.eitherResult $ t ~?> p

        t ~?> p = ALB.parse p t

instance Source Atto.Parser T.Text T.Text AT.Result where
        t ~> p = AT.parseOnly p t

        t ~?> p = AT.parse p t

instance Source Atto.Parser LT.Text T.Text ALT.Result where
        t ~> p = ALT.eitherResult $ t ~?> p

        t ~?> p = ALT.parse p t

-- | Class for generically inspecting unconsumed input
class Leftover r s | r -> s where
        -- | Get the unconsumed input from the result of a parser
        --   
        --   Returns 'Nothing' if the unconsumed input is ""
        leftover :: r a -> Maybe s

instance Leftover AB.Result B.ByteString where
        leftover (AB.Done t _) = Just t
        leftover _             = Nothing

instance Leftover ALB.Result LB.ByteString where
        leftover (ALB.Done t _) = Just t
        leftover _              = Nothing

instance Leftover AT.Result T.Text where
        leftover (AT.Done t _) = Just t
        leftover _            = Nothing

instance Leftover ALT.Result LT.Text where
        leftover (ALT.Done t _) = Just t
        leftover _              = Nothing